Imaging Findings:
A large area of abnormal high signal intensity (and corresponding low signal intensity on the ADC map, not shown, thus representing restricted diffusion) consistent with cytotoxic edema is identified in the left occipital lobe and thalamus on the diffusion weighted scan. Not shown on the images presented, this abnormality extended as well into the medial temporal lobe. There is minimal mass effect. Abnormal high signal intensity is also present on the heavily T2-weighted fast spin echo scan, consistent with vasogenic edema. The occipital lobe, medial temporal lobe, and thalamus are all within the posterior cerebral artery (PCA) territory. Although cytotoxic edema is seen within 15 minutes of ischemia, vasogenic edema occurs later, with 90% of infarcts demonstrating vasogenic edema by 24 hours. This infarct is thus more likely to be > 24 hours in age, and would thus be early subacute (1-7 days) in time frame. Abnormal areas of low signal intensity seen within the occipital lobe on the diffusion weighted scan (less evident, but also present on the T2-weighted scan) are consistent with petechial hemorrhage. Also noted is a tiny chronic lacunar infarct involving the left putamen, seen with abnormal high signal intensity on the T2-weighted scan.